1. Technical Field
The present invention relates to an electrophotographic image forming apparatus, and in particular, to a method for preventing the interior of the image forming apparatus from being contaminated.
2. Related Art
In general, an electrophotographic process is widely employed for an image forming apparatus such as a copier, a laser beam printer (LBP), a LPH (LED Print Head) printer, and a facsimile using a plain paper. Such an electrophotographic process consists of the successive steps of charging .fwdarw.exposing .fwdarw.developing .fwdarw.transferring .fwdarw.fixing.
As discussed in more detail below, prior electrophotographic process is burdened by several disadvantages. Notable among these disadvantages is contamination of the photosensitive drum, causing formation of a background image as well as contamination of the interior of the apparatus. Attempts have been made to solve such problem by including, in the apparatus, a separate blade to clean the photosensitive drum, or by idly rotating the photosensitive drum a specified number of rounds prior to printing so as to clean the drum. However, installation of a separate blade causes increase in the cost of the apparatus and also generates toner waste. Furthermore, rotation of the photosensitive drum reduces printing speed.
Therefore, there is a need for the development of a method for preventing the contamination of a photosensitive drum in an image forming apparatus without waste of toner and without degrading printing speed.
The following patents are considered to be representative of the prior art, and are burdened by the disadvantages set forth herein: U.S. Pat. No. 5,500,720 to Karasawa, entitled Bias Application Control Device For Image Forming Apparatus Using Reverse Development, U.S. Pat. No. 5,339,141 to Suzuki et al., entitled Developing Device With A Developer Carrier Capable Of Forming Numerous Microfields Thereon, U.S. Pat. No. 5,309,207 to Omori, entitled Apparatus For Forming Image, U.S. Pat. No. 4,448,867 to Ohkubo et al., entitled Image Forming Method And Device For Same, U.S. Pat. No. 4,674,860 to Tokunaga et al., entitled Image Transfer Device, U.S. Pat. No. 4,444,864 to Takahashi, entitled Method For Effecting Development By Applying An Electric Field Of Bias, U.S. Pat. No. 4,330,199 to Komori et al., entitled Electrophotographic Device, U.S. Pat. No. 3,918,971 to Zweig, entitled Method For Creating Multiple Electrostatic Copies By Persistent Conductivity, U.S. Pat. No. 3,909,258 to Kotz, entitled Electrographic Development Process, U.S. Pat. No. 4,954,843 to Oka et al., entitled Electrophotographic Image Forming Apparatus, U.S. Pat. No. 4,870,460 to Harada et al, entitled Method Of Controlling Surface Potential Of Photoconductive Element, U.S. Pat. No. 3,722,992 to Zweig, entitled Apparatus For Creating An Electrostatic Latent Image By Charge Modulation, and U.S. Pat. No. 5,708,942 to Sugiyama et al., entitled Developing Device For An Image Forming Apparatus.